The present invention relates generally to the field of tow trucks and more particularly to tow trucks equipped with underlift control systems and methods for use with the same.
Tow trucks have long been used to move other vehicles from one location to another. Tow trucks are most often used when the vehicle being moved has been damaged or disabled such that the vehicle may not move using its own driving or moving components. Tow trucks may be used for other purposes, such as repossession purposes. One category of modern tow truck is a “wheel-lift” tow truck category. Wheel-lift tow trucks operate to tow disabled vehicles by lifting either the front or rear wheels off the ground and towing the partially lifted vehicle on its non-lifted wheels.
The lifting of a pair of wheels is often accomplished using an underlift. An underlift is a system of components configured to engage an underside of a target vehicle's wheels and to lift the end of the vehicle off the ground once engaged. Typical underlift systems include a support arm or lift arm and a boom having vehicle engaging attachments attached to a distal end of the boom extending away from the support arm. To engage a vehicle, an underlift system is usually lowered to a loading position. The loading position is typically a position where the support arm and boom are lowered to the ground such that the boom is close and parallel to the ground. The loading position is also usually a position that has been found to reduce the chance that of damaging the vehicle to be lifted. Once the loading position has been reached, the operator will then engage the vehicle, by, for example, reversing or moving the truck so that the boom with vehicle engaging mechanism is pushed under the car. Other trucks may engage the vehicle in different ways. For example, some trucks may use a winch or other mechanism to pull the vehicle onto the vehicle engaging attachments of the boom. A truck operator may then use lift controls to lift and/or tilt the distal end of the boom up at some angle and to lift and/or tilt the entire underlift structure (i.e., support arm, boom, vehicle engaging mechanism, etc.) up and away from the ground. A tow truck operator thereby engages and lifts structures of a target vehicle off the ground for towing.
While some vehicles are disabled in convenient locations for wheel engagement and lifting, other vehicles are disabled along uneven land or land that is angled downward. For example, if a vehicle is disabled in a ditch or in a driveway having a negative grade, it may be difficult to load the vehicle onto the boom as the boom may extend along a plane parallel to the frame of the tow truck and the distal end of the boom having the wheel engaging mechanism may be higher off the ground than may be desirable. To account for varying ground grades or situations, some modern underlifts have negative tilt capabilities. For example, tow truck models “MPL” and “MPL-40” sold by JERR-DAN CORP. include negative tilt booms. Negative tilt features allow a tow truck operator to position the underlift boom in the optimum position (i.e., level and close to the ground even during negative ground grade situations) for vehicle engagement.
While negative tilt features have certain advantages, the Applicants have discovered that negative tilt features also present certain difficulties or challenges. For example, Applicants have found that underlifts having negative tilt features are more susceptible to underlift mechanism damage. This damage can range from excessive dent and scratch damage that decreases the life-span of underlift components and/or may introduce rust to more serious damage such as the deformation of moving or actuating parts. Negative tilt or lift features may also damage driveway or roadway features and surfaces if the boom is improperly positioned.
What is needed is a vehicle, system and/or method that satisfies one or more of these needs or provides other advantageous features, such as, for example, ease-of-use features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the claims, regardless of whether they accomplish one or more of the aforementioned needs.